diff --git a/packages/mermaid/src/config.spec.js b/packages/mermaid/src/config.spec.js
deleted file mode 100644
index 1f7fd976b3..0000000000
--- a/packages/mermaid/src/config.spec.js
+++ /dev/null
@@ -1,56 +0,0 @@
-import * as configApi from './config.js';
-
-describe('when working with site config', function () {
-  beforeEach(() => {
-    // Resets the site config to default config
-    configApi.setSiteConfig({});
-  });
-  it('should set site config and config properly', function () {
-    let config_0 = { foo: 'bar', bar: 0 };
-    configApi.setSiteConfig(config_0);
-    let config_1 = configApi.getSiteConfig();
-    let config_2 = configApi.getConfig();
-    expect(config_1.foo).toEqual(config_0.foo);
-    expect(config_1.bar).toEqual(config_0.bar);
-    expect(config_1).toEqual(config_2);
-  });
-  it('should respect secure keys when applying directives', function () {
-    let config_0 = {
-      foo: 'bar',
-      bar: 'cant-be-changed',
-      secure: [...configApi.defaultConfig.secure, 'bar'],
-    };
-    configApi.setSiteConfig(config_0);
-    const directive = { foo: 'baf', bar: 'should-not-be-allowed' };
-    const cfg = configApi.updateCurrentConfig(config_0, [directive]);
-    expect(cfg.foo).toEqual(directive.foo);
-    expect(cfg.bar).toBe(config_0.bar);
-  });
-  it('should set reset config properly', function () {
-    let config_0 = { foo: 'bar', bar: 0 };
-    configApi.setSiteConfig(config_0);
-    let config_1 = { foo: 'baf' };
-    configApi.setConfig(config_1);
-    let config_2 = configApi.getConfig();
-    expect(config_2.foo).toEqual(config_1.foo);
-    configApi.reset();
-    let config_3 = configApi.getConfig();
-    expect(config_3.foo).toEqual(config_0.foo);
-    let config_4 = configApi.getSiteConfig();
-    expect(config_4.foo).toEqual(config_0.foo);
-  });
-  it('should set global reset config properly', function () {
-    let config_0 = { foo: 'bar', bar: 0 };
-    configApi.setSiteConfig(config_0);
-    let config_1 = configApi.getSiteConfig();
-    expect(config_1.foo).toEqual(config_0.foo);
-    let config_2 = configApi.getConfig();
-    expect(config_2.foo).toEqual(config_0.foo);
-    configApi.setConfig({ foobar: 'bar0' });
-    let config_3 = configApi.getConfig();
-    expect(config_3.foobar).toEqual('bar0');
-    configApi.reset();
-    let config_4 = configApi.getConfig();
-    expect(config_4.foobar).toBeUndefined();
-  });
-});
diff --git a/packages/mermaid/src/config.spec.ts b/packages/mermaid/src/config.spec.ts
new file mode 100644
index 0000000000..457cb82443
--- /dev/null
+++ b/packages/mermaid/src/config.spec.ts
@@ -0,0 +1,72 @@
+import * as configApi from './config.js';
+
+describe('when working with site config', function () {
+  beforeEach(() => {
+    // Resets the site config to default config
+    configApi.setSiteConfig({});
+  });
+  it('should set site config and config properly', function () {
+    const config_0 = { fontFamily: 'foo-font', fontSize: 150 };
+    configApi.setSiteConfig(config_0);
+    const config_1 = configApi.getSiteConfig();
+    const config_2 = configApi.getConfig();
+    expect(config_1.fontFamily).toEqual(config_0.fontFamily);
+    expect(config_1.fontSize).toEqual(config_0.fontSize);
+    expect(config_1).toEqual(config_2);
+  });
+  it('should respect secure keys when applying directives', function () {
+    const config_0 = {
+      fontFamily: 'foo-font',
+      fontSize: 12345, // can't be changed
+      secure: [...configApi.defaultConfig.secure!, 'fontSize'],
+    };
+    configApi.setSiteConfig(config_0);
+    const directive = { fontFamily: 'baf', fontSize: 54321 /* fontSize shouldn't be changed */ };
+    const cfg = configApi.updateCurrentConfig(config_0, [directive]);
+    expect(cfg.fontFamily).toEqual(directive.fontFamily);
+    expect(cfg.fontSize).toBe(config_0.fontSize);
+  });
+  it('should allow setting partial options', function () {
+    const defaultConfig = configApi.getConfig();
+
+    configApi.setConfig({
+      quadrantChart: {
+        chartHeight: 600,
+      },
+    });
+
+    const updatedConfig = configApi.getConfig();
+
+    // deep options we didn't update should remain the same
+    expect(defaultConfig.quadrantChart!.chartWidth).toEqual(
+      updatedConfig.quadrantChart!.chartWidth
+    );
+  });
+  it('should set reset config properly', function () {
+    const config_0 = { fontFamily: 'foo-font', fontSize: 150 };
+    configApi.setSiteConfig(config_0);
+    const config_1 = { fontFamily: 'baf' };
+    configApi.setConfig(config_1);
+    const config_2 = configApi.getConfig();
+    expect(config_2.fontFamily).toEqual(config_1.fontFamily);
+    configApi.reset();
+    const config_3 = configApi.getConfig();
+    expect(config_3.fontFamily).toEqual(config_0.fontFamily);
+    const config_4 = configApi.getSiteConfig();
+    expect(config_4.fontFamily).toEqual(config_0.fontFamily);
+  });
+  it('should set global reset config properly', function () {
+    const config_0 = { fontFamily: 'foo-font', fontSize: 150 };
+    configApi.setSiteConfig(config_0);
+    const config_1 = configApi.getSiteConfig();
+    expect(config_1.fontFamily).toEqual(config_0.fontFamily);
+    const config_2 = configApi.getConfig();
+    expect(config_2.fontFamily).toEqual(config_0.fontFamily);
+    configApi.setConfig({ altFontFamily: 'bar-font' });
+    const config_3 = configApi.getConfig();
+    expect(config_3.altFontFamily).toEqual('bar-font');
+    configApi.reset();
+    const config_4 = configApi.getConfig();
+    expect(config_4.altFontFamily).toBeUndefined();
+  });
+});
diff --git a/packages/mermaid/src/config.type.ts b/packages/mermaid/src/config.type.ts
index 138eee44f3..3b5826d1ae 100644
--- a/packages/mermaid/src/config.type.ts
+++ b/packages/mermaid/src/config.type.ts
@@ -229,24 +229,24 @@ export interface PieDiagramConfig extends BaseDiagramConfig {
 }
 
 export interface QuadrantChartConfig extends BaseDiagramConfig {
-  chartWidth: number;
-  chartHeight: number;
-  titleFontSize: number;
-  titlePadding: number;
-  quadrantPadding: number;
-  xAxisLabelPadding: number;
-  yAxisLabelPadding: number;
-  xAxisLabelFontSize: number;
-  yAxisLabelFontSize: number;
-  quadrantLabelFontSize: number;
-  quadrantTextTopPadding: number;
-  pointTextPadding: number;
-  pointLabelFontSize: number;
-  pointRadius: number;
-  xAxisPosition: 'top' | 'bottom';
-  yAxisPosition: 'left' | 'right';
-  quadrantInternalBorderStrokeWidth: number;
-  quadrantExternalBorderStrokeWidth: number;
+  chartWidth?: number;
+  chartHeight?: number;
+  titleFontSize?: number;
+  titlePadding?: number;
+  quadrantPadding?: number;
+  xAxisLabelPadding?: number;
+  yAxisLabelPadding?: number;
+  xAxisLabelFontSize?: number;
+  yAxisLabelFontSize?: number;
+  quadrantLabelFontSize?: number;
+  quadrantTextTopPadding?: number;
+  pointTextPadding?: number;
+  pointLabelFontSize?: number;
+  pointRadius?: number;
+  xAxisPosition?: 'top' | 'bottom';
+  yAxisPosition?: 'left' | 'right';
+  quadrantInternalBorderStrokeWidth?: number;
+  quadrantExternalBorderStrokeWidth?: number;
 }
 
 export interface ErDiagramConfig extends BaseDiagramConfig {
diff --git a/packages/mermaid/src/diagrams/quadrant-chart/quadrantBuilder.ts b/packages/mermaid/src/diagrams/quadrant-chart/quadrantBuilder.ts
index 8168551ad4..9c11627620 100644
--- a/packages/mermaid/src/diagrams/quadrant-chart/quadrantBuilder.ts
+++ b/packages/mermaid/src/diagrams/quadrant-chart/quadrantBuilder.ts
@@ -1,7 +1,7 @@
 // @ts-ignore: TODO Fix ts errors
 import { scaleLinear } from 'd3';
 import { log } from '../../logger.js';
-import { QuadrantChartConfig } from '../../config.type.js';
+import type { BaseDiagramConfig, QuadrantChartConfig } from '../../config.type.js';
 import defaultConfig from '../../defaultConfig.js';
 import { getThemeVariables } from '../../themes/theme-default.js';
 
@@ -71,7 +71,8 @@ export interface quadrantBuilderData {
   points: QuadrantPointInputType[];
 }
 
-export interface QuadrantBuilderConfig extends QuadrantChartConfig {
+export interface QuadrantBuilderConfig
+  extends Required<Omit<QuadrantChartConfig, keyof BaseDiagramConfig>> {
   showXAxis: boolean;
   showYAxis: boolean;
   showTitle: boolean;